OpenAPI Type Mismatch with ResponseValidationPlugin

[zacharyhansen]

Environment

Apologies if I am misunderstanding something here but going crazy trying to figure out how to type serialization/deserialization for OpenAPI contracts. Below is a simple reproduction of a created Date field which I believe is incorrectly typed.

https://stackblitz.com/edit/github-wanxqepn-jbdy8pb5?file=src%2Flib%2Forpc.ts,src%2Fplayground-client.ts

  "name": "@orpc/nest-playground",
  "version": "1.13.4",
  "private": true,
  "scripts": {
    "preview": "nest build && unbuild --stub && node dist/main.mjs",
    "start:dev": "nest start --watch",
    "type:check": "tsc --noEmit"
  },
  "devDependencies": {
    "@nestjs/cli": "^11.0.16",
    "@nestjs/common": "^11.1.12",
    "@nestjs/core": "^11.1.12",
    "@nestjs/platform-express": "^11.1.12",
    "@nestjs/schematics": "^11.0.9",
    "@orpc/client": "next",
    "@orpc/contract": "next",
    "@orpc/json-schema": "next",
    "@orpc/nest": "next",
    "@orpc/openapi": "next",
    "@orpc/openapi-client": "next",
    "@orpc/tanstack-query": "next",
    "@orpc/zod": "next",
    "@swc/cli": "^0.7.10",
    "@swc/core": "^1.15.10",
    "@tanstack/react-query": "^5.90.20",
    "@types/express": "^5.0.6",
    "@types/node": "^22.19.3",
    "globals": "^17.1.0",
    "reflect-metadata": "^0.2.2",
    "rxjs": "^7.8.2",
    "source-map-support": "^0.5.21",
    "ts-loader": "^9.5.4",
    "ts-node": "^10.9.2",
    "tsconfig-paths": "^4.2.0",
    "typescript": "~5.9.3",
    "unbuild": "^3.6.1",
    "zod": "^4.3.6"
  }
}

Reproduction

What I have setup to showcase the issue

• added a created?: z.coerce.date() field to the planet schema
• created a non ResponseValidationPlugin and a ResponseValidationPlugin client in playground-client.ts

In the playground you can see that using z.coerce.date() with ResponseValidationPlugin - it still iis typed as string in the tanstack query output.

If we mean to do this when not using ResponseValidationPlugin that may make sense as the field would be a string until it is validated.

However, I would expect that when using ResponseValidationPlugin the types would match type planetOutput = OrpcOutput['planet']['find']; - in the playground you can see OrpcOutput does type it as a Date.

https://stackblitz.com/edit/github-wanxqepn-jbdy8pb5?file=src/lib/orpc.ts,src/playground-client.ts,package.json

Describe the bug

In the playground you can see that using z.coerce.date() with ResponseValidationPlugin - it still iis typed as string in the tanstack query output through it should be Date since we are transforming it.

Additional context

No response

Logs

[unnoq]

Please remove JsonifiedClient

- export const client: JsonifiedClient<ContractRouterClient<typeof contract>> =
+ export const client: ContractRouterClient<typeof contract> =

[zacharyhansen]

Ah! you're a legend - thank you!

for my understanding JsonifiedClient simply converts typings to OpenAPI compatible ones?

Another random question for you - in practive do you think the ResponseValidationPlugin adds a performance hit when considering large tables (i..e long lists of records)?

[unnoq]

ResponseValidationPlugin perform on client so I don't think it is important about performance CPU runtime